AAs the boat weaves between the jagged rocks of the Scilly Archipelago off Cornwall, Round Island, uninhabited except for a lone Victorian lighthouse, comes into view. Those on board preparing for their visit are not armed with cameras and binoculars but with buckets of poisonous grain bait and rat traps.
When signs of rats running amok on the island were first spotted in January 2022, a rescue operation to save the resident seabirds sprang into action. There was only a small window of opportunity to attempt a “total eradication” of rats before the return of Manx shearwaters and storm petrels in April.
“It was an awful feeling because you just know that seabirds that nest in burrows aren’t going to survive with these rats,” says Jaclyn Pearson, islands and biosecurity manager for the RSPB, who found the rats. first signs of invasion. Manx shearwaters and storm petrels “use the same habitat – a rat will descend into that hole where the bird lays its eggs. If the rats were not entirely eliminated by the time the birds laid their eggs, all the chicks would be eaten.
Pearson is one of six members of Biosecurity for life, a squad of elite conservationists stationed across the UK with a mission to save seabirds from invasive species incursions into our island habitats. “We hold the world’s population of Manxies along the UK’s west coast islands,” she says. “They have a very specific habitat. These islands have the right kind of vegetation – birds can dig burrows near the sea, they can go out and fish, and are far from predators. In the South West we have the only two colonies in England, on Scilly and Lundy. Round Island is a very precious island.
Armed with a playbook authored by Elizabeth (Biz) Bell, a senior conservationist at Wildlife Management International, based in New Zealand and a specialist in removing invasive species from the islands, Pearson set about mobilizing local volunteers. “I was overwhelmed by the number that came up,” she says.
During the Guardian’s trip to the island in March, Stu Barrs, a local paramedic, was among those willing to scour the grounds for signs of remaining rats. “It is an area of exceptional beauty. If you don’t protect all the things that are here from invasive things, they will lose some of their luster,” he says.
After the perilous climb from the landing craft and the rusty ladder that clings to the rocky ledge of the island, it doesn’t take long to discover signs of the rats’ continued presence: at the top of the climb, marks signs are etched into a flavored block of wax used to monitor rodent activity.
Undeterred, the volunteers set to work scouring the island, freshening baits and luring rats into traps with smears of peanut butter. Efforts are made to target only rats and not harm other species. “We are very careful about mitigating against non-target species. We do everything we can to minimize these risks,” says Pearson.
With its sheer cliffs rising from the sea and glistening in the sun, it’s easy to see why the shearwater travels from as far as the Patagonian plateau to get to Round Island, which is 400 meters (1,300 feet) tall. from one end to the other. However, the viability of such a habitat relies on species reproducing without fear of invasive predators. Norway rats are not native to the UK; they are thought to have arrived in the 1700s and spread across the world from North Asia along sea routes. The rapid reproduction and omnivorous diet of rats can pose catastrophic problems for wildlife that did not evolve alongside them.
Between January and April, Pearson and more than 35 volunteers working in conjunction with the Isles of Scilly Wildlife Trust were able to land on Round Island 13 times. But with weeks of bad weather repeatedly preventing landings, anxiety within the team grew as the deadline approached. “When you’re doing this job, you have to get rid of all the rats,” says Pearson. “You can’t leave one because in six weeks they reproduce. You can get your original number back in a few months.
With just a few days left before the birds were expected to return, the team finally stopped finding any more signs of rats. During the penultimate visit, a camera trap that had repeatedly indicated the presence of what was thought to be the last “fussy” rat on the island showed one of the first returning shearwaters using the burrow like home. “We did it!” Pearson said. “We scoured this island – we would know if there were any more rats there.”
The team was thrilled; returning seabirds will now have a chance to breed with young that may reach adulthood. “The fact that this happened just in time for the island’s breeding bird pairs to have a chance… It’s pretty amazing,” Barrs said.
Previous rat removals on Scilly have shown there is reason to be optimistic about Round Island’s future.
According to Dr Vickie Heaney, seabird ecologist for the Isles of Scilly Wildlife Trust, a similar mission to St Agnes and Gugh in 2013 resulted in an increase in Manx shearwater numbers from 20 breeding pairs to just over 80 , with 53 chicks fledging last. single year. Petrels are up to 30 or 40 pairs.
“It’s absolutely clear that getting rid of the rats has made a huge difference to the seabirds – they haven’t bred on St Agnes and Gugh at all,” Heaney says.
Another successful mission on Lundy in 2004 resulted in a nearly 2,000% increase in Manx shearwaters, and the seabird population has tripled. “We want to take the species recovery course that took place in Lundy,” says Pearson.
Although eradicating rats from the islands is not a magic bullet to turn the tide of Britain’s beleaguered seabirds, it is an achievable step with tangible results. Bell says, “A lot of things impact seabirds, but predation is something we can deal with. We have the technology to eradicate harmful species like rodents, so it’s an easy first step compared to political will regarding climate change, massive pollution events and fishing.
“I would like to see policy changes on those other factors as well, but those will take longer,” Bell adds. “Eradication can be done in a few months.”
Meanwhile, Pearson is watching for signs of revival on the Round Island and there has been some good news on the scilly shrew.
“We know from the data that Scilly’s shrews have been around for a long time. This is an endemic species that lives on Scilly and at the start of this work we couldn’t find any shrew tooth marks on any of the tools,” says Pearson.
‘But on the last two trips we have started to find teeth marks on the non toxic chocolate wax and I think the same is happening as happened in St Agnes in 2013. When we removed the rats, the number of shrews began. increase very rapidly.